Wall Framing Calculator
US & CanadaEnter the wall length, spacing, corners and openings to get the studs and plates to buy, with a stud size check against the IRC or NBC table.
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Layout studs in a door or window opening are left in the count to cover cripples and sills (our assumption). Headers are sized from span tables and are not included.
How the stud count works
- Layout studs = wall length ÷ spacing, rounded down, + 1
- Corners = corners × extra studs per corner (1 by default, so each corner has the NBC minimum of 2)
- Openings, IRC = 1 jack stud + the full-height studs from Table R602.7.5, each side
- Openings, NBC = 2 studs each side, or 3 where the lintel is over 3 m
- Plates = wall length × 3 rows (1 bottom, 2 top), or × 2 with a single top plate
Layout studs that fall inside a door or window are left in the count; they cover the cripples above the header and below the sill. That is our assumption, not a code figure. Headers and their size come from span tables and are not counted here.
Layout studs by wall length
Calculated: layout studs only, before corners and openings.
| Wall | 16 in | 24 in | 400 mm | 600 mm |
|---|---|---|---|---|
| 8 ft (2.44 m) | 7 | 5 | 7 | 5 |
| 10 ft (3.05 m) | 8 | 6 | 8 | 6 |
| 12 ft (3.66 m) | 10 | 7 | 10 | 7 |
| 16 ft (4.88 m) | 13 | 9 | 13 | 9 |
| 20 ft (6.1 m) | 16 | 11 | 16 | 11 |
| 24 ft (7.32 m) | 19 | 13 | 19 | 13 |
| 30 ft (9.14 m) | 23 | 16 | 23 | 16 |
| 40 ft (12.19 m) | 31 | 21 | 31 | 21 |
Stud size and spacing: IRC 2021
From Table R602.3(5), maximum spacing in inches. Bearing studs are limited to a 10 ft laterally unsupported height; non-bearing 2 × 4s to 14 ft and 2 × 6s to 20 ft, at up to 24 in.
| Wall carries | 2 × 4 | 2 × 6 |
|---|---|---|
| Roof and ceiling only | 24 in | 24 in |
| Roof plus one floor | 16 in | 24 in |
| Roof plus two floors | Not listed | 16 in |
Footnote c: a habitable attic on 2 × 4 studs is limited to a 32 ft roof span; beyond that, use 2 × 6 or an engineered design. 2 × 3 studs "shall not be used in exterior walls".
Stud size and spacing: NBC 2020
From Table 9.23.10.1, exterior walls, as printed: maximum spacing and maximum unsupported height.
| Wall carries | 38 × 89 mm (2 × 4) | 38 × 140 mm (2 × 6) |
|---|---|---|
| Roof and ceiling only | 600 mm, 3.0 m | See table |
| Roof plus one floor | 400 mm, 3.0 m | 600 mm, 3.0 m |
| Roof plus two floors | 300 mm, 3.0 m | 400 mm, 3.6 m |
The table also lists 38 × 64 mm at 400 mm (2.4 m) under a roof only, 64 × 89 mm at 400 mm (3.0 m) with two floors, and 38 × 140 mm at 300 mm (1.8 m) with three floors. "See table" means that size has no separate row for that load in the part we read. Interior wall rows are left out on purpose: the PDF text merged some cells, so confirm interior walls against the printed table. Ontario's amendments re-issue Table 9.23.10.1 with the same exterior values.
Studs at openings: IRC Table R602.7.5
Minimum full-height studs at each end of a header in an exterior wall, in addition to the jack stud(s).
| Header span | Under 140 mph Exp. B or 130 mph Exp. C | 115 mph or less, Exp. B |
|---|---|---|
| 4 ft (1.22 m) | 1 | 1 |
| 6 ft (1.83 m) | 2 | 1 |
| 8 ft (2.44 m) | 2 | 1 |
| 10 ft (3.05 m) | 3 | 2 |
| 12 ft (3.66 m) | 3 | 2 |
| 14 ft (4.27 m) | 3 | 2 |
| 16 ft (4.88 m) | 4 | 2 |
| 18 ft (5.49 m) | 4 | 2 |
For spans between rows, the table's footnote says use the larger span. The second column assumes jack studs, not framing anchors.
Sources
- International Residential Code 2021, Chapter 6: Table R602.3(5) Size, Height and Spacing of Wood Studs; R602.3.2 Top plate; R602.3.4 Bottom (sole) plate; R602.7.5 Supports for headers and Table R602.7.5 (ICC Digital Codes public view, November 2021 version). https://codes.iccsafe.org/content/IRC2021P2/chapter-6-wall-construction
- National Building Code of Canada 2020, Division B, Part 9: 9.23.10.1 and Table 9.23.10.1 Size and Spacing of Studs; 9.23.10.5 (corners); 9.23.10.6 Studs at Sides of Openings; 9.23.11.2 Bottom Wall Plates; 9.23.11.3 Top Plates; 9.23.11.4 Joints in Top Plates (1st printing, NRC 2022). https://publications.gc.ca/collections/collection_2022/cnrc-nrc/NR24-28-2020-eng.pdf
- Ontario amendments to the National Building Code of Canada 2020 (O. Reg. 163/24), MMAH, version dated October 21, 2025, item 484 (Article 9.23.10.1). https://www.parrysound.ca/media/sy2fhdzc/ontario-amendment-document-oct-21-2025.pdf
Stud counts, metric equivalents of inch spacings (16 in = 406.4 mm, 24 in = 609.6 mm) and plate lengths are calculated. NBC values are from the 1st printing; check the 2nd printing (errata of March 31, 2025) for any change to Table 9.23.10.1.